Estrogen biosynthesis is catalyzed by the Aromatase (P450arom), which is derived from CYP19A1. We investigated the relationship between actin filament re-arrangement, CYP19A1 expression and estradiol bio-synthesis in bovine granulosa cells in vitro. Both bovine fibroblasts and granulosa cells were starved in serum-free culture medium for 24 hours. Serum-starvation disassembled stress fibers in fibroblasts, but not in granulosa cells. Additionally we added Y27632 and CB to medium to de-polymerize the actin filaments, while LPA and insulin were used to re-polymerize actin filaments. A real-time RT-PCR analysis revealed that, FSH induced transcription of CYP19A1 mRNA encoded aromatase was inhibited significantly as actin filaments were de-polymerized by both Y27632 and CB, whereas, restored as actin filaments were re-polymerized by both LPA and insulin. However, further study shows that, statistically there were no differences in the expression of aromatase proteins analyzed by western-blot, during the process of actin filament rearrangement. ARIA analysis also indicated that the secretions of estradiol by bovine granulosa cells were not changed significantly. The results suggested that serum-starvation could not induce actin filaments depolymerization in bovine granulosa cells, while chemically induced actin filament rearrangement influenced the expression of aromatase in mRNA level. But there were no differences in protein level and biological activity of bovine granulosa cells in vitro.

Key words: Actin filament, Bovine FSH, Estradiol, Granulosa cell, Polymerization